1. Technical Field
The present invention relates generally to a dispensing apparatus and more particularly to a robot-actuated dispensing station for dispensing a variety of similarly dimensioned objects.
2. Discussion
The implementation of robots to automate various manufacturing processes has dramatically increased in an effort to reduce the labor and production costs associated with these processes. Robots now perform many of the more hazardous and highly repetitive operations in the manufacturing process. These operations include dispensing, deburring, grinding, polishing, painting, finish coating, cutting and welding. Robots are capable of achieving even greater efficiency when several of these operations are combined at a single workstation. For example, providing a robot with welding and grinding tools allows a single robot to first weld the workpiece, and then grind the workpiece as necessary at a single workstation. For even greater efficiency, the same robot may be equipped with an optical system for finally inspecting the quality of the finished weldment. Robots may also be used to assemble various components, measure or inspect the tolerances of these components, and finally perform any necessary adjustments to the subassembly for completing the requisite operations.
An exemplary implementation of robots for automating an assembly operation is the assembly of the components associated with an automobile rear end axle. Conventional assembly techniques require that a shim or adjusting washer be placed on the pinion stem between the pinion gear and the pinion's conical bearing. A shim of the correct thickness must support the pinion gear on the inner race of the conical bearing for properly positioning the pinion gear within the rear axle housing.
In an exemplary assembly process, a partially assembled rear axle housing travels along a palletized conveyor and enters an assembly and gaging station. The parts to be assembled are contained on the pallet. A robot located within the workstation places the conical bearing upon the gage head. At this point, no shim is present between the gage head and conical bearing. As the robot moves away from the subassembly, a gaging mechanism is lowered onto the conical bearing for measuring the various tolerances associated with the subassembly. At this point, the gaging station is capable of calculating the proper thickness shim which must be placed between the pinion gear and conical bearing. As this occurs, the gaging mechanism is lifted away from the subassembly and a call for a particular shim is sent to the robot's controller. The robot then moves to a static dispensing station located in the cell and selects the correct size shim.
The robot presents the shim to the automated verifier. If this thickness is correct, or within accepted tolerance levels, the robot selects the verified shim and places the shim on the pinion stem. The robot removes the conical bearing from the gage head and sets the conical bearing on the pinion stem and moves away from the subassembly. If the tolerances are within the acceptable range, the gaging mechanism is lifted away and the pallet moves toward the next workstation. If the tolerances are unacceptable, the pallet can be rejected, or the components disassembled so that the assembly process can again be cycled.
The conventional technique for supplying the robot with the correct thickness shim was to locate a motorized and automated dispensing apparatus within the workstation. The conventional dispensing apparatus utilized a round, rotary table having a plurality of storage tubes mounted at the perimeter. Each storage tube was then filled with a stack of shims having the same thickness. Rotation of the table was controlled by a programmable servo-driven gear box for rotating the table to align the proper storage tube over a fixed position powered escapement. Once the proper tube was correctly aligned, the powered escapement was actuated for dispensing the shim into a shim thickness verifier. After measuring and verifying the correct shim thickness, the robot could select the shim from the verifier and place it onto the subassembly. This conventional design was based upon many tubes which were actuated by a single powered escapement.
While this conventional technique for dispensing similarly dimensioned parts automates the dispensing process, this automated technique also duplicates several of the functions which can be performed by the robot for achieving greater efficiency. In addition to the expense associated with the electronically controlled robot, the rotary indexing table also requires expensive electronic equipment and control systems for powering and automating the rotary table. Further, the conventional rotary table shim dispensers utilize a single universal escapement which must be capable of accommodating all sizes of shims. Such a design can lead to jamming of the shims within the escapement, which requires intervention by an operator, and may lead to assembly line shutdown. Further, cycle time associated with a rotary table varies from cycle to cycle, and is dependent upon the distance the table must rotate. Accordingly, an assembly process dependent upon a rotary dispensing table must be designed to operate at the longest cycle time, rather than upon a constant cycle time. An additional disadvantage is that when a wide range of different sized shims must be dispensed, the rotary table circumference increases and requires a large area of the manufacturing floor. Adding a second table increases floor space demands and doubles the cost for equipment. Finally, the robotic manufacturing cell and rotary table must be shut down in order to restock the storage containers with a new supply of shims. All of these factors significantly increase the cost associated with the manufacturing cell and automated dispensing apparatus. These considerations also contribute to the reliability of the apparatus, and the skill level of the operator required for maintaining the automated dispensing apparatus.
Accordingly, it is desirable to provide a dispensing station which can overcome the complexity and cost problems associated with conventional shim dispensing stations and maximizes the use of the robot's features. It is also desirable to provide a low cost shim dispensing station which eliminates the need for powered components, and does not require wires, switches, or other manufacturing facility utilities. Such a device would eliminate the need to have air hoses, steam lines, and multiple electrical lines brought into the manufacturing cell to power the dispensing station. Further, it is desirable to provide a dispensing station which can be refilled with components without shutting off the power, or interrupting the production line. As the cycle times within the manufacturing cell are an increasing concern, it is desirable to provide a dispensing station for reducing the cycle time required to dispense the individual components. Further, it is desirable to provide a dispensing station which can dispense more components using less floor space. Finally, it is desirable to provide a dispensing station having individual escapements which can be custom sized to accommodate the part or shim that is stored in that escapement's storage container.